High-Intensity Flashlamp Photoepilation

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Abstract
SEVERAL DEVICES for removing undesired hair by the delivery of radiant energy to the skin (photoepilation) are currently in clinical use or under investigation. With all these photoepilation systems, it is hypothesized that melanin in the follicular epithelium or hair shaft absorbs radiant energy, thereby mediating follicular damage1-3 and resultant cessation of hair growth.4-8 However, the precise mechanisms responsible remain unclear. Photoepilation could induce a prolonged, telogen-type quiescent state, possibly involving a program of apoptosis or dysregulation of the cell cycle; according to that hypothesis, reversion to an active anagen state might then account for the late recurrence of hair growth observed with the use of some photoepilation devices.8 Alternatively, the absorption of energy might induce destructive photothermal or (less likely in the case of long-pulse duration) photomechanical effects, causing follicles to undergo nonspecific cell death or oncosis9 and eventuating in generalized follicular necrosis and resorption. Some authors propose that photoepilation may involve short-term growth delay and long-term clinical hair loss. The latter may be caused by miniaturization of hairs to a velluslike state.10 These various mechanisms may not be mutually exclusive. By optimizing exposure factors such as pulse duration and wavelength, it may be possible to vary these effects to achieve a better therapeutic index.